code: def generate_useless_category() -> DataFrame:
      return Series(
          [
              "a",
              "b",
              "c",
              "d",
              "e",
              "f",
              "g",
              "h",
              "i",
          ],
          name="cat_useless",
      ).to_frame()
  
imports: import copy
  import numpy
  import pandas
  import pytest
  from pandas import DataFrame, Series
  from autogluon.common.features.feature_metadata import FeatureMetadata
  from autogluon.features.generators import AbstractFeatureGenerator
label_desc: Use image node_id 15 for calling the DataHelper obj's underlying member method code with example usage: obj.generate_useless_category() and returns: Series